Gas manufacture



May 29, 1956 E. R. RETAILLIAU 2,748,179

GAS MANUFACTURE Filed Oct. 25, 1951 3 Sheets-Sheet 1 May 29, 1956 EQ R. RETAILLIAU GAS MANUFACTURE Filed Oct. 25, 1951 W WQOCLOQOE Pan-mwa Feen cnvewraoTo @As Edmand Q. QetcmLL nu. :mveaor United States atenf GAS MANUFACTURE Edmond R. Retailliau, Crantord, N. J., assigner to Esso Research and Engineering Company, a corporation of Delaware Application October 25, 1951, Serial No. 253,108

9'Claims. (Cl. 26th-673) The-present invention relates to the oxidation of rela tively low molecular Weight hydrocarbons. More -particularly, the present invention relates to the conversion ofl relatively low molecular weight hydrocarbons which are normally resistant to reforming reactions, into products valuable asfuel and as intermediates for conversion into products of high octane value. Morespecifically, the present invention relates to the generation of city gas and-hydrocarbon synthesis gas comprising hydrogen and carbon monoxide, as well as the preparation of valuable olens and armomatics, by oxidative cracking ofsaid low molecular weight hydrocarbons in the presence of gaseous oxygen in the combustion space of a cyclically operating unred internal combustion engine.

Whereas it is. well-known in the art that hydrocarbon material: may be reacted-with oxygen to yield various oxygenated .compounds-as well as hydrocarbons vof lower molecular weight, great dimculties have been encountered in attempting to carry out-such reactions on a commercial scale; This is largely due to the fact that the reactions. of oxygen withhydrocarbons are highly exothermic and that the heat thus evolved is locally so highv as to cause many undesirable side reactions with the result that the yields of the desirable products are extremely low, usually less than.l.0% on the hydrocarbon feed. In the few cases where such oxidation has been carried out in commercial plants, it has been found necessary to dilute the reactants with enormous amounts of unreactive diluent materialV in order to obtain some control of the reaction towards forming the desired compound. The size of' the` equipment required is very large with regard to-the volume of the chemical compound produced and its cost consequently extremely high; because of this, the oxidative treatment of hydrocarbon material has found applicationonly in cases where the relatively high value of 'the oxygenatedcornpound obtained could provide some return on the investment. lt has now-been found'that-conversion of cheap hydrocarbon material by a comparatively inexpensive oxidationprocedure may be performed so asfto give relatively high yields of valuableproducts such` as aromatic and -olelinic hydrocarbons together with some. oxygenated compounds such as carbonyls and alcohols. As the source of hydrocarbon material, there may be employed either gaseous hydrocarbons such as methane; ethane and propane or liquid hydrocarbons such as n-"bu'` tane, n-pentane, n-hexane and the like, which do not'lend themselves' easily to reforming processes and these are converted in good yields to thevabove mentioned classes of valuable compounds. The light unsaturated hydrocarbons arev particularly valuable for alkylating purposes andi thus willcontribute to increase the supply of aviation blending agents as will the aromatics produced in'the'proc-'- ess. On the other hand, the process may be so operated as to: produce a mixtureY of hydrocarbons highly suitable' In accordance with the present invention, a low molec--I ular weight hydrocarbon, such as n-pentane for example,

ice

is vaporized and blended with a predetermined amount of oxygen-bearing gas such as ordinary air, although pure oxygenimay be used for certain purposes if desired. This mixture is then-conditioned by a suitable heat treatment prior to being conducted into the cylinder of a compressor or of an unired reciprocating engine where, as a result of the heat generated by compression of said mixture, the hydrocarbonis brought to a satisfactory level of activation for causingit to react with the oxygen present and produce a gas eminently suitable for use asA city gas. The B. t. u. value-of the gas so produced is controlled by thequantity of oxygen-containing gas added and by the choice of oxygen or air. With the use of air, the diluent nitrogen serves to reduce the B. t. u. value to the values used in city gas distribution which is usually around 500B. t. u. On the other hand, if desired, a high B. t'. u. gas suitable Vfor the replacement'of natural gas can be obtained by partial or complete removal of the nitrogen diluent by the additional use of suitable absorption processes or 4by usingfsteam instead of nitrogen as diluent.

The lack of availability of fuel gasor city gas at isolated points has long been felt. It has not been feasible to build pipe lines or mains from centers wherein gas pro.- ducer units are located, todistant areas. The use of compressed city or natural gas is cumbersome and not feasible on a large scale. By operating in'accordance with thepresent invention, by setting up: a compressor, or series of compressors or engines, at isolated points, manufactured gas of any desired B. t. u. value may be produced in Avolume suitable for the load conditions required.y

Particularly useful as the hydrocarbon in this operationy aref the normally low molecular weight liquid hydrocarbo11s,=suchl as n-pentane, n-hexane, and the like. These hydrocarbons are dicult to convert into useful products;` for instance,it is-either extremely diliicult or impossible-to-convert n-pentane into a cyclic hydrocarbon by hydroforming or reforming and it is very difiicult to perform this operation lon n-hexane. In the past, these materials have been employed for solvents or they have been subject to isomerization reaction and thus converted into a gasoline blending agent. ln accordance with the presentinvention, this type of hydrocarbon is oxidatively cracked in the' compressors located at isolated spots, whereby a large supply of manufactured gas is thus available without the heavy cost entailed in building coal gas manufacturing plants or the cost of constructing gas mains andlines and piping gas largeV distances.

The 'size of compressors required to produce such gas by' 'the process to be described in detail below is moderate. Thus, a single compressor having about 'a 131/2 inch piston diameter and a 20 inch stroke and operatingat 200 Ri P. M. will produce over a million cubic feet per day of gas; if two or three compressors are employed, their size would be correspondingly smaller. Smaller compressors would also be employed if higher compression speeds are used. The cost of a single compressor for producing a million cubic feet per day is in the range of about $15,000 to $20,000 and tlius, it is readily 'seen that the process of the invention provides a convenient and inexpensive method of supplying small communities with mamifacturedv gas. Also, if lit is'contemplated to employ the manufactured gas as hydrocarbonsynthesis gas, i. e. gas mixture comprising essentiallyof carbon monoxide `and hydrogen which is catalytically converted into high octane motor fuel by passage over a 'group VIII catalyst, this affords another means of converting Va low octane hydrocarbon into a high octane material;

.ilthoughfthe exact mechanism byA which n-pentane is converted by Ioxygen into a multiplicity of other cornt gen, methane and aromatics were found) is not thoroughly understood, it is believed that the initial reaction of the pentane with Yoxygen results in the formation of peroxides at a certain stage of the compression stroke when the activation of the molecules has reached a suicient level. These peroxides, in turn, decompose upon further heating (as the compression stroke proceeds farther) to yield a number of free radicals and the reaction then proceeds at an accelerated rate by a chain mechanism process. Because of the deficiency of the mixture in oxygen, a large proportion of the free radicals formed from the decomposition of the peroxides combine with one another to form stable hydrocarbon or other molecules such as methane, ethylene, benzene, or hydrogen, etc., rather than reacting7 with additional oxygen. The identication of benzene and toluene in the reaction products is indicative of the formation of highly dehydrogenated radicals such as :CH- or -CH=CH, etc., which have combined to form the stable aromatic nucleus. However, the present invention is not intended to be dependent upon this or any other possible explanation of the reaction mechanism.

An important feature of the invention is that an unfired rather than a iired engine is employed. The reason for this is that use of an electric spark for promoting the reaction of oxygen with the hydrocarbon always results in the formation of increased amounts of carbon dioxide without appreciably increasing the hydrocarbon conversion. The net effect of sparking the hydrocarbon-air mixture being to convert part `of the desirable carbon monoxide initially formed into useless carbon dioxide, it is obviously advantageous to prevent such product degradation and hence, operation of the engine without spark is a valuable feature of the present invention. lf, however, it is desired to increase the production of carbon dioxide as, for example, for the supplemental manufacture of Dry Ice, a spark could then be used without departing from the principles of this invention.

The reaction within the engine is critically sensitive to temperature, contact time, compression ratio, and above all, to the ratio of oxygen t-o hydrocarbon. A relatively long contact time or low R. P. M. of the driving motor produces carbon dioxide and Water rather than a fuel gas. A high preheat temperature, for instance, above about 400 F., causes a pre-reaction which may have an unfavorable effect. A low proportion of oxygen such as below an 0.5 mol ratio, shows little reaction at 350 F., whereas almost complete utilization of the oxygen is obtained at 1.0 ratio and above. However, large carbon formation resulted from operation at 2.0 mol ratio. Furthermore, as detailed more fully below, in a systematic series of experiments made at 1.0 oxygen to hydrocarbon mol ratio (that is, with oneeighth the theoretical amount of oxygen required for complete combustion of this particular hydrocarbon) at 400 F. intake temperature, during which the compression ratio was increased in small increments, it was shown that there was practically no reaction until a certain critical temperature is reached at which the reaction proceeds with an explosive velocity. Under the experimental conditions employed, this critical compression temperature was calculated from the actual peak compression 'of the air-fuel mixture to be 898 F. and was reached at a compression ratio of 9.49 to l. Thus, during most of the compression or at low compression ratios, there is no reaction and only when compression is brought to that stage high enough for the heat generated to activate the reaction are desired reaction products obtained. Thus, by operating in accordance with the present invention, the prerequisite of an extremely short reaction time followed by extremely rapid cooling is obtained. These are not available with ordinary equipment.

The process of the invention may best be illustrated in accordance with the Figure l which shows one embodiment of the present invention. For the purpose Iof the example, normal pentane is employed though it will be understood that other hydrocarbons such as the normally gaseous parainic hydrocarbons or normally liquid parainic hydrocarbons as n-butane, n-hexane and the like, or liquid naphthenic hydrocarbons may also be used.

The n-pentane is pumped from storage tank 1 through lines ll and l2 to a metering device 3, and thence through line 14 to heat exchanger 4 where it is vaporized; the ilow of pentane is regulated by means of valve 2 and by-pass line 13 through which the excess pentane is returned to the storage Vessel l. From heat exchanger 4, the vaporized pentane is led through line 15 into a mixing chamber 5 where it is blended with the required amount of air (or oxygen, if desired) bled from storage tank 7 through line 16 and valve 8 into the metering device 9 and thence through line 17 into mixer 5. This mixing vessel may be of any conventional design for intimately blending gaseous components and, for example, may be of the ejector or carburetor type. The gaseous mixture of pentane vapors and oxygen-containing gas is then preheated to a predetermined temperature in heat exchanger 6 and thence conducted through line 18 into the intake manifold of the compressor or of the unred single or multicylinder engine 10 (or a battery of such compress-ors or engines) employed for causing the hydrocarbon to react with the oxygen by compression of the heated mixture. The pistons of these compressors or engines are externally actuated to provide for alternate compression and expansion of the reacted gases. This may be achieved by any suitable means such as an electric motor or diesel engine, etc. Inasmuch as the present invention does not reside in the type of engine used, the latter will not be described in detail, but is of conventional design save for the fact that spark plugs or other means of ignition are not essential; for example, single cylinder or multi-cylinder engines of the diesel or spark ignition types or 4-cycle compressors are suitable for the purpose of the invention.

Following the reaction occurring during the compression stroke, the gaseous mixture produced is partially cooled during the expansion stroke and then expelled during the exhaust stroke, the jacket cooling medium temperature being adjusted to leave suicient heat in the exhaust gases for adequate preheating of the incoming feed. The hot exhaust gases are thus conducted countercurrently to the incoming feed in heat exchangers 4 and 6 through lines 19 and 2l and are finally cooled in condenser 24 which may be `of any ,desired conventional design employing any suitable coolant. The cooled gases are then separated from the condensed hydrocarbons in gas separator 26 from which both products are sent to their respective storage tanks, the condensed liquid to tank 30 through line 28 and the gas to gas holder 29 through line 27. Suitably located valves such as valves 20, 33 and 34 are used for regulating the amount of exhaust gas diverted to the heat exchangers as required to preheat the incoming mixture to the desired temperature.

A single cylinder CFR engine, equipped with either the regular CFR head for determination of octane numbers of motor gasolines or with a diesel head, was used for demonstrating the process using substantially the layout shown in Figure l, except that the heating of vessels 4 and 6 was obtained by electrical means rather than by 5 oxygenibearin'g gaseous .mediumfutiliz'e'd in: thisrworks f In orderffmore readily to establish thel variousreactionsoc-y curring during the -oxidation of hydrocarbons,` -n-pentane of high purity (better than 99.0% pure) was employed in most of this Work although lightV Virgin fractions which are extremely refractory to reforming processes were alsov successfully used. A considerable number of experiments were performed for the systematic investigation. of the influence of the many variables involved in thisV novel method. of hydrocarbon conversion.

Briefly summarized, it was discovered using a 4-stroke cycle engine, that longreaction times resultingrfrom 'very low engine speeds, as from 20 R. P.. M..to about 200 R. P. M., were unfavorable since a large proportion ofthe oxygen used was converted to carbon dioxide, an undesirable product from the point of View of the present invention.' On the other hand,rspeeds from 200 to 900 R. P. M. were highly satisfactory and preferably engine'speeds of from`200 to 300 R. P. M. are used. Since in' a 4-stroke cycle engine one compression stroke occurs for everytwo revolutions of the engine crankshaft, these' engine speeds correspond to 100-450 and to 100-150' compressions per minute, respectively. In a 2-stroke cycle engine, the revolutions of the engine per minute are the same numerically as the number of compression strokes per minute. Although the engine jacket temperature may be varied from about 200 to 500 F., temperatures of from 250 to 350 F. arer more advantageous and similarly preheating of the hydrocarbon-air mixture to from about 200 to 400 F. is

preferred, although higher temperatures may be useful inv certain cases. The importance of properly choosing the compression ratio at which to carry out the oxidation reaction is best emphasized by the data plotted in Figs. 2V

and 3, from which it is seen' that, with the engine employed in this particular series of tests, activation of the reactants requires a minimum compression ratio of at least about 9.5:1 and that further increases in compression' ratiov brought only relatively insignicant additional changes in the various products.

As indicated previously, the ratio of oxygen. to hydrocarbon is highly critical with regard to the end products obtained. For the preparation of a city gas, for example, there is used an amount of lair which will give anoxygen to hydrocarbon ratio of from about 0.5 to about 1.5, and preferably about 1.0 whereas, if it is desired to prepare a synthesis gas for use in the manufacture of synthetic gasolines by the Fischer-Tropsch process,`the proportion of oxygen is increased and there is used air in amounts corresponding to about from 1.5 to 2.8 mols of oxygen per mol of hydrocarbon; preferably about 2.0 molsof.

oxygen per mol of hydrocarbon in the case of n-pentane, which was used in the present case, since these proportions give hydrocarbon-air mixtures safely above the upper explosive limit of n-pcntane. It will be noted that an oxygen to pentane mol ratio of 1.0 corresponds to l12.5%

of the amount required for complete combustion of pen-- tane to carbon dioxide andwater, While a ratio of 2.8

corresponds to 35% of this theoretical amount. In the commercial application of the process, safety devices Well knownin the art vwould naturally be used for automatic control of the respective llows of reactants and prevention of the formation of explosive mixtures.

Having thus fully described the various effects of themain variables involved in the operation of the. process,- there will now be described the properties of the products obtained. As examples, there are shown the production of a city gas and of a synthesis gas which were obtainedl under the same engine operating conditionsexcept for'tlie:

fact that the oxygen to pentane mol ratio was different. Typical products are presented in TableY I, following:

Manufac ture of Synthesis Gas Manufacture of City Gas ee (b) Gaseous Phase, `VolumeA Percent ct Feed 8l. 3 82.6

Properties of Liquid:

Bromine Number, cg./g Saponication Number. Neutralization Number. Specific Gravity, 60/60.;

COMPOSITION OF. DRYEXHAUST GAS (BYMASS SPECTRO GRAPH) M01 Percent Percent Hydrogen Methane I Ethylene. Propylene. Carbonl Monoxide (By Infrared); Carbon Dioxide'. Nitrogen Oxygen..

From the above composition and B. t. u. value of the` individual components, itV is readily calculated thatthe' city gas produced has an approximate value of 467 B. t'. u. per cubic foot; it can readily be enriched to the desired valuerof- 550B. `t. u./cubic foot by addition of 2.7%J of pentane'.

It 'isof great interest to note that the amount of carbon dioxide produced was very small in both casesand that, therefore, the'oxygen Was employed almost quantitatively for useful purposes; the fact that the city gas produced in this manner is, for'all practical purposes, oxygen-free, is quite important. sinceit makes it quite safe yfor usein cold climatesv in contrast to some other methods previously disclosed where air is blended with gaseous and condensa'- ble hydrocarbons.

It should be further vpointed`- out that, while air was usedas the `source of oxygen in the example given above, the invention'is by notmeans restricted to. such source of oxygen. gas, and the like, may be used for the purpose of the present invention without departing from its spirit and, for example, should a gas ofl greater heating value bedesired, steam would be used as the preferred diluent for" the oxygen-bearing gas. It Will'be obvious that when steam is the diluent, the gaseous hydrocarbon'mixture will bemost readily separated from the condensed steam and a gas of heating value far in excess of that of'natural gas willbe produced by this process.

Finally but not least important is the fact that the liquid hydrocarbon layer recovered is. a most valuable by-product since it containsA a large proportion of-v aro-l compounds (including those recovered from thesmallA amount of water condensed together with the hydrocarbon layer) and 1.8%v-of mono-olefins which are valuable addition agents for4 motor. gasoline.Since'f all thesefconstituents -of vthe "hydrocarbon layer may be readily separated by simplefra'ctionation from the unreacted pentane- Indeed, other diluents, carbon dioxide,. ue..

which constitutes the remaining part of the hydrocarbon layer, it is seen that a relatively important source of revenue is available which will make the manufacture of city gas by this procedure relatively inexpensive and well adapted to the purpose intended. The unreacted pentane so separated can either be used for increasing the heating value of the city gas manufactured when using air as the source of oxygen-bearing gas or may be recycled to the process for the further production of additional city gas.

The formation of aromatics is favored when about 1 mol oxygen per mol pentane is employed in the engine or compressor and when the dilution of the oxygen with an inert gas is relatively small, being from about 4 to 8 times its own volume. Onthe other hand, if the molar ratio of oxygen to pentane is doubled but the dilution of the oxygen with an inert gas is simultaneously considerably increased to about 14 to 18 times its own volume, the pentane or other paratlinic hydrocarbon may be converted to a substantial extent, to the corresponding olefin, as well as other valuable products without degradation to methane, carbon dioxide and light parafns. Although oxidative dehydrogenation of parafns has been known for years, it has not been used on a cornmercial scale because of the very low yields of the desired olens obtainable and because of the large extent of degradation of the original paraffin to useless gaseous products such as CO2, CH4 and the like. By contrast, a substantial amount of the paraffin is converted to the corresponding olefin by means of the present process without significant degradation to undesirable products but with the production of lower oleiins which are particularly advantageous for the manufacture of high octane gasoline components by the conventional alkylation or polymerization processes. feed to a CFR engine equipped with a diesel head and operating this engine as a compressor, in the presence of two mols of oxygen (air) per mol of pentane and 200% dilution of the air with nitrogen (or steam) and preheating the whole gaseous mixture to 200 F., before entering the engine cylinder, and operating at a compression ratio of 11.5, there was converted 31% of the npentane in a single pass, the amount of pentenes formed amounting to about 21% of the pentane converted. At' the same time, about 41% of other valuable oletins, suclr as ethylene, propylene and butylenes and 25% of valuable oxygenated hydrocarbons were formed. This is summarized in Table II.

TABLE Il Selectivz'ty of n-pentanve to various compounds under conditions of controlled oxidation Experimental conditions:

Diesel head-4300 R. P. M.-11. compression ratio 200F.- intake and 350F. jacket temperature 2.0 oxygen/pentane mol ratio 200% nitrogen dilution of air intake lroducts recovered:

1911 cubic feet of exhaust gas 1425 ml. of aqueous solution 495 ml. of hydrocarbon layer Peutane conversion:

30. 98% on pentane feed or 36. 45% ou pentane accounted for by recovered products. Selectivity:

.Percent of pentane A. To carbon oxides: reacted CO2 3.82 O 7. 64 B To olefin Ethlene. 15. 29 Propylene 17. 32 Butylenes. 7. 64 Pentenes 21. 36 Hexenes 0.22

C. To Parallns: Hexaues 1. 89

I). To oxy compounds as a group 24. 79

or individually:

To Acids as acetic acid Aldehydes as formaldehyde Kctones as MEK Alcohols as butyl alcohol E. Summary: selectivity to olens oxy compounds 86.62%

Thus, using pentane as the 3 This process, therefore, provides a valuable means for converting normal parafns which have little value as motor fuel components into derivatives of far greater value. its versatility is well demonstrated by the fact that oleins and oxygenated compounds are produced under the conditions just described without degradation to useless compounds, whereas, under diterent conditions, aromatics are obtainable besides providing the synthesis gas or city gas described in Table l.

What is claimed is:

l. An improved process for converting low molecular weight, normally liquid hydrocarbons into valuable, predominantly hydrocarbon fuels, which comprises the steps of preheating to a temperature in the range of 200-400 F. a gaseous feed mixture comprising said hydrocarbons and a limited amount of a free oxygen-containing gas, the ratio of free oxygen to hydrocarbon being in the range of about 0.5 to 2.8 mols of oxygen per mol of hydrocarbon, and being insufficient to support complete cornbustion; passing at least a portion of said mixture to an externally unheated reaction zone; compressing said mixture in said zone rapidly to about 1/10 to 1/20 of the original volume of said reaction zone about to 450 times a minute for a reaction period of less than about 0.005 minute so that its temperature is increased substantially exclusively by said compression to a level conducive to a limited reaction during said compression between the hydrocarbon and the free oxygen to produce carbon compounds having less hydrogen per molecule than the hydrocarbon; rapidly thereafter expanding the reaction products to reduce their temperature; and withdrawing reaction products from said zone having a greater number of molecules than the gaseous feed mixture, and comprising valuable, predominantly hydrocarbon fuel products.

2. The process of claim l wherein said mixture of oxygen and hydrocarbon is diluted with an inert gas.

3. The process of claim 1 wherein said inert gas is steam.

4. The process of claim l nitrogen.

5. The process of claim 1 wherein said hydrocarbon is a low octane, low molecular weight parainic compound having up to 6 carbon atoms in the molecule.

6. The process of claim 1 wherein said mixture is compressed to 21AM, of its original volume.

7. The process of claim l wherein said oxygen-containing gas is air, diluted with added nitrogen to the extent of about 200%.

8. The process of claim l wherein steam is added to said feed mixture.

9. The thermal process of converting a low molecular weight normally liquid hydrocarbon feed stock containing parainic hydrocarbons to produce a hydrocarbon mixture of improved motor fuel value without substantial degradation to methane, which comprises preheating to about 200 to 400 F. a feed mixture of said hydrocarbon and an oxygen-containing gas, the ratio of oxygen to hydrocarbon in said mixture being between about 1.5 and 2.8/1, rapidly compressing said mixture to a maximum of 1/10 of its original volume and maintaining the compressed mixture at an elevated temperature due to said compression for a period of less than about 0.005 minute, thereafter rapidly cooling tbe resultant mixture including reaction products containing an increased number of molecules as compared to the feed mixture by expanding, and recovering therefrom a product including a normally liquid hydrocarbon fraction produced'during the compressionl step of improved octane value having a wherein said inert gas is substantially increased total content of olenic and aro-l matic hydrocarbons.

(References ou following page) References Cited in the le of this patent UNITED STATES PATENTS Klein et al. Ian. 10, ,193.9

10 Kipper Feb. 24, 1942 Frey Nov. 7, 1944 FOREIGN PATENTS Great Britain June 26, 1924 

1. AN IMPROVED PROCESS FOR CONVERTING LOW MOLECULAR WEIGHT, NORMALLY LIQUID HYDROCARBONS INTO VALUABLE, PREDOMINANTLY HYDROCARBON FUELS, WHICH COMPRISES THE STEPS OF PREHEATING TO A TEMPERATURE IN THE RANGE OF 200* -400* F. A GASEOUS FEED MIXTURE COMPRISING SAID HYDROCARBON AND A LIMITED AMOUNT OF A FREE OXYGEN-CONTAINING GAS, THE RATIO OF FREE OXYGEN TO HYDROCARBON BEING IN THE RANGE OF ABOUT 0.5 TO 2.8 MOLS OF OXYGEN PER MOL OF HYDROCARBON, AND BEING INSUFFICIENT TO SUPPORT COMPLETE COMBUSTION; PASSING AT LEAST A PORTION OF SAID MIXTURE TO AN EXTERNALLY UNHEATED REACTION ZONE; COMPRISING SAID MIXVOLUME OF SAID REACTION ZONE ABOUT 100 TO 450 TIMES A MINUTE FOR A REACTION PERIOD OF LESS THAN ABOUT 0.005 MINUTE SO THAT ITS TEMPERATURE IS INCREASED SUBSTANTIALLY EXCLUSIVELY BY SAID COMPRESSION TO A LEVEL CONDUCTIVE TO AN LIMITED REACTION DURING SAID COMPRESSION BETWEEN THE HYDROCARBON AND THE FREE OXYGEN TO PRODUCE CARBON COMPOUNDS HAVING LESS HYDROGEN PER MOLECULE THAN THE HYDROCARBON; RAPIDLY THEREAFTER EXPANDING THE REACTION PRODUCTS TO REDUCE THEIR TEMPERATURE; AND WITHDRAWING REACTION PRODUCTS FROM SAID ZONE HAVING A GREATER NUMBER OF MOLECULES THAN THE GASEOUS FEED MIXTURE, AND COMPRISING VALUABLE, PREDOMINANTLY HYDROCARBON FUEL PRODUCTS. 